Low Output Alternator.

[Brian422]

Beta43 Starter Alternator.

Alternator low output voltage when engine running (12.86 volts).

Voltage on B Terminal 1.2 volts when engine stopped.

Removing cable from B terminal and measuring voltage on cable 12.6 volts.

Suspect regulator.

I'd be grateful for any advice or guidance.

[Tracy D'arth]

12 minutes ago, Brian422 said:

Beta43 Starter Alternator.

Alternator low output voltage when engine running (12.86 volts).

Voltage on B Terminal 1.2 volts when engine stopped.

Removing cable from B terminal and measuring voltage on cable 12.6 volts.

Suspect regulator.

I'd be grateful for any advice or guidance.

There must be a really bad connection to your battery for this to be so.

[Bargebuilder]

What was the voltage of the battery before you started charging it? A flatish battery may be dragging down the voltage.

Were the engine revs high enough for the alternator to be able to achieve its optimum output?

[Brian422]

Battery voltage 12.63 volts which is present on the cable end when it has been disonnected from the B Terminal; something inside Alternator dragging down voltage?

W

Engine rev 1500.

Edited July 12, 2022 by Brian422
Add '?'

[Tracy D'arth]

8 minutes ago, Brian422 said:

Battery voltage 12.63 volts which is present on the cable end when it has been disonnected from the B Terminal; something inside Alternator dragging down voltage?

W

Engine rev 1500.

Your meter does not draw sufficient current to see voltage drop through a poor connection, only an open connection.

[Tony Brooks]

Assuming the B+ terminal is properly crimped onto the conductor and the connector to the alternator is tight this makes no sense. What have you connected the meter negative lead to and is it clean?

If it is an internal alternator short pulling the voltage down on the thick cable then the alternator case should be very hot with the engine stopped until the battery goes flat. (Make sure the relevant master switch is in good order - put both leads on one terminal post and remeasure).

[Brian422]

1 minute ago, Tracy D'arth said:

Your meter does not draw sufficient current to see voltage drop through a poor connection, only an open connection.

My meter is a DVM with very high input restance so will have no effect on voltage.

12.63 volt on end of disconnected cable; agreed there's no DVM will draw enough current.

An open connection would give no voltage at cable end.

 

[Tracy D'arth]

6 minutes ago, Brian422 said:

My meter is a DVM with very high input restance so will have no effect on voltage.

12.63 volt on end of disconnected cable; agreed there's no DVM will draw enough current.

An open connection would give no voltage at cable end.

 

You did not understand but never mind.

[ditchcrawler]

1 hour ago, Tracy D'arth said:

There must be a really bad connection to your battery for this to be so.

How about a diode splitter? Would that indicate a very low voltage

[Tony Brooks]

15 minutes ago, ditchcrawler said:

How about a diode splitter? Would that indicate a very low voltage

 

The normal way of wiring one would give zero or very close to zero voltage on the B+ alternator terminal unless the alternator was charging. Ditto on the end of the disconnected B+ cable.

 

That 1.62 volts to a DVM I find puzzling.

[nicknorman]

3 hours ago, Brian422 said:

Beta43 Starter Alternator.

Alternator low output voltage when engine running (12.86 volts).

Voltage on B Terminal 1.2 volts when engine stopped.

Removing cable from B terminal and measuring voltage on cable 12.6 volts.

Suspect regulator.

I'd be grateful for any advice or guidance.

Not quite specific enough to give a conclusive comment: 12.86v engine running - where? Batteries or alternator B+?

1.2v on B+ terminal engine not running - ignition switched on or off?

 

Also, how does the engine alternator warning light behave? Should be on with ignition on and engine not running, then go out when engine is running.

 

Beta 43 has been around for a good while, with different alternators, but I think mostly the engine alternator is a 6 diode machine whereby the field current comes from the B+ and thus from the battery initially. So for example if there was a high resistance connection between the battery and B+ (and the battery isolator switch is the most likely cause) and with the ignition on engine not running,  telling the alternator to start working, it would be trying to take a few amps down the B+ wire and if there was a high resistance connection there would be a big voltage drop, hence the 1.2v. When the wire is disconnected, no current flowing hence the 12.6v.

 

Bottom line is that if there is around 12.6v at the battery and only 1.2v at the alternator in what should just be a straight and nominal zero resistance connection, well that is impossible, so there must be a high resistance somewhere between the two. Could possibly be in the negative, not necessarily in the positive (although in the positive is more likely).

[Brian422]

10 hours ago, ditchcrawler said:

10 hours ago, ditchcrawler said:

How about a diode splitter? Would that indicate a very low voltage

 

 

Boat has electric Bow Thruster and Sterling Split Charge Diode Isolator so being puzzled decided to dig a little deeper.

 

Three posts on isolator, the middle being mark with red paint whilst the remaing posts are offset.

 

Measured voltages before disconnecting to check diodes (Engine Stopped).

Middle post (red paint) 2.91 volts and connected to Starter Alternator.

Left Hand post 12.63 volts connected to Starter Battery.

Right Hand post 11.82 volts connected to Bow Thruster Battery.

 

There's also a 15 amp fuse connected between middle post and right hand post; suspect feed to Bow Thruster Control Panel.

 

Individual diodes pass DMV diode check; approx 460 Ohms in forward direction and infinite in reverse with no leakage to case.

 

From what I can gather fromYou Tube, Middle Post with red paint should go to Starter Battery with Sarter Alternator and Bow Thruster Battery supply connected seperately to either of the remaining post. This would appear incorrect, however, when engine running Starter Alternator should provide voltage supply from middle post via forwad biased diodes to both Starter and Bow Thruster Batteries. 

This configuration would explain why voltage on Starter Alternator B Terminal appears low.

 

These connections are as made when boat was built!

 

All suggestions gratefully recieved apart from need for 'Girlie Button'.

 

 

Edited July 13, 2022 by Brian422
Added details.

[Tony Brooks]

2 hours ago, Brian422 said:

 

Boat has electric Bow Thruster and Sterling Split Charge Diode Isolator so being puzzled decided to dig a little deeper.

 

Three posts on isolator, the middle being mark with red paint whilst the remaing posts are offset.

 

Measured voltages before disconnecting to check diodes (Engine Stopped).

Middle post (red paint) 2.91 volts and connected to Starter Alternator.

Left Hand post 12.63 volts connected to Starter Battery.

Right Hand post 11.82 volts connected to Bow Thruster Battery.

 

There's also a 15 amp fuse connected between middle post and right hand post; suspect feed to Bow Thruster Control Panel.

 

Individual diodes pass DMV diode check; approx 460 Ohms in forward direction and infinite in reverse with no leakage to case.

 

From what I can gather fromYou Tube, Middle Post with red paint should go to Starter Battery with Sarter Alternator and Bow Thruster Battery supply connected seperately to either of the remaining post. This would appear incorrect, however, when engine running Starter Alternator should provide voltage supply from middle post via forwad biased diodes to both Starter and Bow Thruster Batteries. 

This configuration would explain why voltage on Starter Alternator B Terminal appears low.

 

These connections are as made when boat was built!

 

All suggestions gratefully recieved apart from need for 'Girlie Button'.

 

 

 

 

 

For a typical passive split charge diode the middle one is fed from the alternator and the other two feed their respective batteries. They should be marked on the case The diodes isolate the two battery connections from each other. This means that with the engine off there should be zero volts on the alternator terminal. You seem to have 1.6V so unless you have  a leaky diode I can't explain why. It might be an active electronic split charge "diode" like a Driftgate 2000, but they should not put voltage on the alternator connection, but they might.

 

With the engine running and alternator energised you should get alternator voltage on the alternator connection.

 

Be wary about U tube videos unless you already know what you are looking at or they are posted by the manufacturer or a well respected source.

 

How about a photo of this diode?

[David Mack]

4 hours ago, Brian422 said:

Middle post (red paint) 2.91 volts and connected to Starter Alternator.

Left Hand post 12.63 volts connected to Starter Battery.

Right Hand post 11.82 volts connected to Bow Thruster Battery.

 

There's also a 15 amp fuse connected between middle post and right hand post; suspect feed to Bow Thruster Control Panel.

 

If there is a fuse connecting the middle and right hand posts then the voltage on these two should be the same. So is the fuse blown? Or are the contacts dirty? What type of fuse is it? The bullet type are known for their unreliable contact.

[Brian422]

It is said that the learning curve is steep.

Getting on the bottom is difficult enough however I know more about Split Charge Diode Isolation and the layout of my boats' electrics. Also have removing alternator down to a fine art 😉.

Happy to report Starter Alternator Regulator replaced; B Terminal 13.88 volts engine running, 0 volts engine stopped.

Thank you all for your help and guidance.

Regards

Brian.